linux-kernel - Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error

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Message-ID: <CAMj1kXG53RH0vJZnWJWi8KSQ6aA0uxi_uhYnffeO5+85ZTYZnA@mail.gmail.com>
Date:   Tue, 10 Nov 2020 08:45:30 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel
 compilation error

On Tue, 10 Nov 2020 at 08:44, Dmitry Osipenko <digetx@...il.com> wrote:
>
> 09.11.2020 10:25, Ard Biesheuvel пишет:
> ...
> >>> So the options are
> >>>
> >>> a) merge my patch that adds 2 bytes of opcode to the Thumb2 build
> >>> b) merge Dmitry's patch that adds an unconditional literal load to all builds
> >>> c) remove kernel mode handling from vfp_support_entry() [my other patch]
> >>> d) move sections around so that vfp_kmode_exception is guaranteed to
> >>> be in range.
> >>> e) do nothing
> ...
> >> The performance argument is questionable to me, to be honest. In
> >> practice the performance difference should be absolutely negligible for
> >> either of the proposed options, it should stay in a noise even if
> >> somebody thoroughly counting cycles, IMO.
> >>
> >> I'm still thinking that the best option will be to apply a).
> >>
> >
> > Can we take that as an acked-by?
>
> Are you asking me for the ack?

Yes.

> I think this is a more appropriate
> question to Russel. I'm not arm/ maintainer, but could give r-b and t-b.
>

R-b and acked-by are basically the same thing.

> If you're going to follow approach that I'm suggesting with a) + d),
> then could you please resend the two patches in a single series? The
> first one-line patch-fix should contain the fixes tag.

Ok